April 2^, 1889] 



NATURE 



609 



pumps to make them quite secure against the most 

 extensive damage to their bottoms. Indeed, as regards 

 the stoke-holds, they are already fitted with the air-tight 

 hatches in order to be able to used forced draught for 

 the furnaces. Modern merchant ships are built with 

 an iron deck, so that there is no difficulty about pro- 

 viding the strength. Their hatchways are, however, 

 always very large ; but, on the other hand, there is little 

 traffic through them, so that they could be treated in a 

 more substantial way than the smaller hatchways of a 

 man-of-war with her large complement of men. The 

 bulkheads which subdivide the hold into compartments 

 always profess to be water-tight, and to be able to resist 

 the pressure exercised by the water filling the compart- 

 ment. There should therefore be no difficulty about 

 them. Indeed, if ships were built to withstand air 

 pressure, a very simple method would be provided for 

 testing the efficiency of the bulkheads without the dis- 

 agreeable process of filling the compartment with water. 

 It would be only necessary to close the legitimate open- 

 ings and get the air in it up to a pressure equal to that of 

 the ship's draught of water, and the result would be 

 unequivocal. It is proper to observe that the construc- 

 tion of an air-tight bulkhead would differ slightly from 

 that of a water-tight bulkhead, inasmuch as it will be 

 exposed to the maximum pressure over its whole surface, 

 whereas the water-tight bulkhead is exposed to a 

 graduated pressure, being greatest at the keelson, and 

 least under the deck. 



A further advantage of fitting a ship with air-tight sub- 

 divisions is, that it not only gives her greater security 

 against foundering, but it affords a means of largely 

 insuring her against risks of fire. This has more 

 especial reference to merchant ships. If the contents of 

 a ship's hold catch fire, the easiest way of putting it out 

 is to stop the supply of air, and this can be done if the 

 hold is air-tight. 



So far the damage to the ship is supposed to be a rent 

 in the bottom. If it is not in the bottom, but somewhere 

 above it, then the air can only expel the water down to 

 the level of the breach, when the air will begin to escape 

 through its uppermost part. It will now depend on the 

 supply of forced air available, how large a hole can be 

 kept continuously filled by a stream of air rushing out. 

 The area so occupied is necessarily closed to the entrance 

 of water, and if the machinery can supply air at a suffi- 

 cient rate, the whole rent can be filled by a current of 

 air, which, so long as it is kept up, is as efficient a leak 

 stopper as a plate of iron would be, and meantime the 

 bottom of the hold can be cleared by the ordinary bilge 

 pumps. 



Rents in a ship's side, such as are produced when she 

 is run down, or rammed by another, are usually so 

 extensive and serious that, unless the ship is protected by 

 an inner skin, immediate destruction ensues before there 

 is time to take any measures for rescuing her. But with 

 an inner skin the damage may be so far reduced as to 

 make it possible to deal with it as above indicated. The 

 higher up on the ship's side is the damage the less suit- 

 able is the pneumatic method for dealing with it, if it 

 is of a really extensive character ; but, on the other hand, 

 the more easy is it (given the time) to get at it, and deal 

 with it from the outside. In all cases where the ship has 

 been damaged by touching the ground, or by torpedo 

 explosion under the bottom, and not involving the de- 

 struction of the ship, the pneumatic method affords the 

 readiest means of combating the results. 



It must be remembered that a ship's hold when filled 

 with compressed air will be habitable; that is, if an air 

 lock is provided, men can descend into it and repair the 

 damage, just as they can descend into a caisson and dig 

 out the foundations for the pier of a bridge. 



The pneumatic method is however not only adapted 

 for keeping damaged vessels afloat, it is also useful for 



raising sunken or stranded ships. For this purpose the 

 salvage steamer must be provided with air-forcing pumps 

 as well as the suction pumps which she usually carries. 

 Having closed, and if necessary strengthened the deck, 

 by means of divers if below water, she then pumps air 

 into the holds of the ship, and at once restores a large 

 proportion of her original buoyancy to her. If she does 

 not rise, the other methods of salvage can be applied in 

 addition, and with much increased chance of success. 



The principle of this method is not new. A very old 

 device in endeavouring to float, or to keep afloat, ships, is 

 to fill as much of their damaged hold as possible with 

 empty casks. A later modification of this method is to 

 use inflatable india-rubber bags. It may be remembered 

 that after the Vanguard sank Admiral Popoff of the 

 Russian Navy sent a large apparatus of this kind in 

 order to render assistance in trying to float her. Both 

 these appliances are cumbersome. A ship's hold is 

 seldom quite empty when she sinks, and even if it 

 were, it is not easy to fill it under water with casks full of 

 air, or even with inflatable air bags ; and in any case 

 it is difficult in this way to fill more than a fraction of the 

 hold with air. The simple and efficient way of dealing 

 with the matter is to treat the ship's hold itself as the 

 vessel to be filled with air. 



Compressed air is every day occupying a wider field as 

 a means of transmitting power. It is already used as a 

 substitute for gunpowder in the guns for firing shells with 

 high explosives. It seems to me that if it can be used 

 for largely increasing the safety of life and property at 

 sea it is right that the fact should be brought as 

 prominently forward as possible, in the hope that it may 

 receive practical application in the hands of the ship- 

 builder and the engineer. J. Y. Buchanan. 



NOTES ON STANLEY'S JOURNEY. 



I HAVE watched every footstep of Stanley for the past 

 twenty years, had constant intercourse with him 

 during his short visits to this country, and have un- 

 bounded confidence in him as a pioneer, for I 

 cannot but admire the noble efforts he has made to 

 open up Africa to civilization. Wherever he has tra- 

 velled he has left his mark behind him ; others may 

 follow his example without fear of being molested, 

 and he has given us such vivid descriptions of the 

 regions mapped by him that, for all practical purposes, no 

 traveller need supervise his work. Some say he has been 

 too high-handed with the natives, but I may be allowed to 

 think that his power of influencing those over whom he 

 holds command has proved him to be the most trusted 

 and successful traveller of the age. If his explorations 

 be quickly and judiciously followed up, the native in- 

 habitants will feel security against all oppression, and the 

 traders in slaves will be expelled from the country. 



Brilliant is scarcely the name to give the exploit of Mr. 

 Stanley, as given in his recently published letters. What 

 instance in travel can excel such devotion ? Is there a 

 schoolboy who does not admire a man with his indomit- 

 able pluck and dogged perseverance ? His latest journey 

 to relieve Emin Pasha has outstripped, if possible, all his 

 previous explorations in the " Dark Continent." Those 

 160 days of toil, from June 28 to December 12, 1888, 

 through starvation, desertion, mutiny, savage dwarfs 

 and cannibals, thorny thickets, darkness, and swamps, 

 were enough to try the patience of any human being ; 

 but, thank God, his British pluck never failed him ; on 

 and on he pressed, while his native followers were in utter 

 despair, and broke out into mutiny. He used every per- 

 suasion with them : all failed. What was he to do ? He felt 

 that his duty was to relieve Emin Pasha — his countrymen 

 expected this — and, with his accustomed sense of what was 

 just and right, the two ringleaders of the mutinous band 



